Second law of thermodynamics would like to chime in, even with such a perfect nonexistent power source, waste heat is still an issue… which you can radiate to space, which would take tremendous land use to facilitate…
Or we use that land and capital and effort for solar power, which exists and could power practically everything in our lives, minus AI. Sounds like a win to me.
(Also not to mention the necessity to fire up more fossils for this shit to compensate for the current lack of miracle power for their pipe dreams)